Methods for the production of cathode materials for lithium ion batteries

ABSTRACT

The present disclosure provides methods for producing cathode materials for lithium ion batteries. Cathode materials that contain manganese are emphasized. Representative materials include Li x Ni 1−y−z Mn y Co z O 2  (NMC) (where x is in the range from 0.80 to 1.3, y is in the range from 0.01 to 0.5, and z is in the range from 0.01 to 0.5), Li x Mn 2 O 4  (LM), and Li x Ni 1−y Mn y O 2  (LMN) (where x is in the range from 0.8 to 1.3 and y is in the range from 0.0 to 0.8). The process includes reactions of carboxylate precursors of nickel, manganese, and/or cobalt and lithiation with a lithium precursor. The carboxylate precursors are made from reactions of pure metals or metal compounds with carboxylic acids. The manganese precursor contains bivalent manganese and the process controls the oxidation state of manganese to avoid formation of higher oxidation states of manganese.

RELATED APPLICATION INFORMATION

This application is a divisional of and claims priority from U.S. patentapplication Ser. No. 16/416,236, filed May 19, 2019, the disclosure ofwhich is hereby incorporated by reference.

GOVERNMENT RIGHTS

This invention was made with government support under ContractDE-SC0017761 awarded by the Department of Energy. The government hascertain rights in the invention.

FIELD

The present disclosure relates to cathode materials for lithium ionbatteries. More particularly, the present disclosure relates to methodsfor producing transition metal oxide materials. Most particularly, thepresent disclosure relates to methods for preparing oxide materials withlayers of lithium that alternate with layers of oxides of nickel,manganese, and/or cobalt (“NMC”), or nickel and manganese without cobalt(“NM”), or nickel, manganese and/or cobalt and/or other elements. Thematerials feature a controlled degree of mixing of transition metalcations in the lithium layers and minimization of the presence of Mn⁴⁺and higher oxidation states of manganese during the synthesis.

BACKGROUND

Electric vehicles (EVs) represent safe, quick, quiet, robust andenvironmentally desirable means of transportation among most commuters.However, they account for a tiny fraction of automotive sales, mainlybecause the batteries are expensive and need to be recharged frequently.In order to meet the United States Advanced Battery Consortium (USABC)goals for advanced batteries for EV and facilitate more rapid marketpenetration of EV, the technology requires a significantly reducedbattery cost and increased material performance.

Lithium ion batteries (LIBs) are rechargeable batteries that generateelectrical current when lithium ions shuttle to and fro between a pairof electrodes. LiNi_(1−x−y)Mn_(x)Co_(y)O₂ (NMC) and LiNi_(1−x)Mn_(x)O₂(LNM) with layered structures, and Li_(x)Mn₂O₄ (LM) andLi_(x)Mn_(2−y)Ni_(y)O₄ (LMN) with spinel structures, have been the majorcathode materials, while graphite has been the typical anode material.The lithium cathode materials are responsible for about 40% of the costof the battery. The current manufacturing cost of NMC materials is highdue to the use of conventional hydroxide co-precipitation method ofsynthesis. This multi-step process is complicated and expensive.

Many difficult problems have been encountered in developing nextgeneration battery materials—in part due to an incomplete understandingof reaction mechanisms. For example, the simple and low-cost solid-statesynthesis process has worked well for the industrial production ofLiCoO₂ (LCO) and LiNi_(0.8)Co_(0.15)Al_(0.05)O₂ (NCA), but has not yetbeen employed in mass production of the NMC materials. Here we brieflydiscuss the differences between the two materials based on theirchemistry and structure.

Although LiCoO₂ has high power performance, it delivers a low 140mA-hr/g of storage capacity because only about half of the Li atoms areutilized. Both LiNiO₂ and LiMnO₂ have the same layered structure asLiCoO₂. LiNiO₂ has high reversible capacity, but suffers from poor cyclestability and low rate. In LiMnO₂, a larger amount of Li atoms are ableto reversibly deintercalate/intercalate to the structure. However,during cycling, the layered structure LiMnO₂ tends to transform to thecubic spinel structure LiMn₂O₄, leading to significant capacity loss. Amultiple cation layered structure phase, i.e.,LiNi_(1−x−y)Mn_(x)Co_(y)O₂ (NMC), could provide the advantages of eachof the pure cation phases while overcoming many of the drawbacks.

In addition to crystal structure, the performance of cathode materialsfor lithium batteries depends on morphology. Reducing the particle sizeis critical to improving the rate performance by shortening the lithiumdiffusion distance and enlarging the contact area with the electrolyte.The use of nanostructures is an effective way to improve the kinetics oflithium ion transport and enhance the electrochemical performance of thecathode material. Layered NMC nanostructures with differentmorphologies, such as nanorods, porous nanorods, nanoparticles,microspheres, hollow microspheres, and microcubes, are interestingbecause they display high performance. These nanostructured materialscan be synthesized by various methods, such as hydroxideco-precipitation, carbonate co-precipitation, combustion, solid statereaction and spray-drying methods.

Known solid state reaction methods for the production of NMC cathodesinclude reacting a mixture of cobalt-, manganese-, nickel- andlithium-containing oxides or oxide precursors (such as the processdescribed in U.S. Pat. No. 7,488,465 by Eberman, entitled “Solid statesynthesis of lithium ion battery cathode material”). This productionprocess is less efficient and high cost because it uses expensivetransition metal precursors as the starting materials. The production ofthe solid state precursors is a complicated, multistep process, whichconsumes a significant amount of chemicals and energy. Furthermore, thisconventional solid state process is difficult to control.

SUMMARY

The disclosure presents methods for the production of cathode materialsfor lithium ion batteries. Manganese-containing cathode materials, suchas NMC (LiNi_(1−x−y)Mn_(x)Co_(y)O₂), LM (Li_(x)Mn₂O₄) and LNM(Li_(x)Ni_(1−y)Mn_(y)O₂), are emphasized. These cathode materialsfeature high energy density. The process comprises reacting a mixture ofnickel, manganese, cobalt, and/or lithium precursors and calcining toform an oxide.

The precursors for nickel, manganese, and cobalt are carboxylates.Preferred carboxylates are acetates and citrates. Precursors for lithiuminclude lithium hydroxide and lithium carbonate.

The metal carboxylate precursors are prepared from metal startingmaterials that enable a reduction in the cost of production of thecathode materials. Metal starting materials include pure metals andmetal compounds. Metal compounds include oxides, hydroxides, andcarbonates.

The metal carboxylate precursors are prepared by reacting a metalstarting material with a carboxylic acid. Reactions include liquid phasereactions and solid state reactions. Liquid phase reactions includemixing a metal starting material with a liquid carboxylic acid or asolution containing a carboxylic acid. Solid phase reactions includegrinding a metal starting material in the presence of a carboxylic acid.Mixed metal precursors are prepared by including two or more metalstarting materials in the reaction.

Metal carboxylate precursors are reacted to form an oxide material.Reactions for forming the oxide material include liquid phase reactionsand solid state reactions. In liquid phase reactions, liquid phase metalcarboxylate precursors are combined, stirred and heated to form aslurry. The slurry is dried, ball milled, and calcined to form a metaloxide. A lithium precursor can be included in the slurry before dryingor added to the slurry after drying, but before ball milling. Solidphase reactions include ball milling solid phase metal carboxylateprecursors in the presence of a lithium precursor and then calcining toform a metal oxide. Metal carboxylate precursors with one or acombination of two or more metals are used in the liquid or solid phasereactions.

The present disclosure extends to:

A method for forming an oxide material comprising:

-   -   reacting a first precursor with a second precursor, said first        precursor comprising a first compound, said first compound        including a first metal bonded to a first carboxylate group and        a second carboxylate group, said second precursor including a        second compound, said second compound including a second metal        bonded to a third carboxylate group.

The present disclosure extends to:

A method of making a carboxylate compound comprising:

-   -   reacting a first pure metal with a first carboxylic acid in the        presence of an inorganic acid.

The present disclosure extends to:

A method of making a carboxylate compound comprising:

-   -   reacting a first metal compound with a first carboxylic acid,        said reacting including ball milling a mixture of said first        metal compound and said first carboxylic acid.

The present disclosure extends to:

A method for forming an oxide material comprising:

-   -   reacting a first precursor with a second precursor, said first        precursor comprising a first compound and a second compound,        said first compound including a first metal bonded to a first        carboxylate group and said second compound including said first        metal bonded to a second carboxylate group, said second        precursor comprising a third compound, said third compound        including a second metal bonded to a third carboxylate group.

The present disclosure also provides a method for directly recycling andregenerating manganese-containing NMC, LMO and LMN cathodes from wastelithium ion batteries, avoiding a complex separation process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows XRD (X-ray diffraction) Rietveld refinement patterns ofsamples of LiNi_(0.5)Mn_(0.3)Co_(0.2)O₂ andLiNi_(0.6)Mn_(0.2)Co_(0.2)O₂.

FIG. 2 shows XRD (X-ray diffraction) Rietveld refinement patterns ofsamples of LiNi_(0.7)Mn_(0.15)Co_(0.15)O₂ andLiNi_(0.8)Mn_(0.1)Co_(0.1)O₂.

FIG. 3 shows SEM (Scanning Electron Microscope) images ofLiNi_(0.5)Mn_(0.3)Co_(0.2) O₂ in an as prepared state.

FIG. 4 shows SEM (Scanning Electron Microscope) images ofLiNi_(0.5)Mn_(0.3)Co_(0.2)O₂ after grinding.

FIG. 5 shows SEM (Scanning Electron Microscope) images ofLiNi_(0.6)Mn_(0.2)Co_(0.2)O₂ in an as prepared state.

FIG. 6 shows SEM (Scanning Electron Microscope) images ofLiNi_(0.6)Mn_(0.2)Co_(0.2)O₂ after grinding.

FIG. 7 shows charge and discharge capacities ofLiNi_(0.5)Mn_(0.3)Co_(0.2)O₂.

FIG. 8 shows rate performance of LiNi_(0.5)Mn_(0.3)Co_(0.2)O₂.

FIG. 9 shows charge and discharge capacities ofLiNi_(0.6)Mn_(0.2)Co_(0.2)O₂.

FIG. 10 shows cycle performance of LiNi_(0.6)Mn_(0.2)Co_(0.2)O₂.

FIG. 11 shows XRD (X-ray diffraction) patterns (without Rietveldrefinement) of a sample of LiNi_(0.5)Mn_(0.2)Co_(0.2)Fe_(0.1)O₂.

FIG. 12 shows XRD (X-ray diffraction) patterns (without Rietveldrefinement) of a sample of LiNi_(0.7)Mn_(0.3)O₂.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The instant disclosure provides a process for producing cathodematerials for lithium ion batteries. The cathode materials containmanganese (Mn) and are produced in high yield at low cost.Representative cathode materials include NMC(LiNi_(1−x−y)Mn_(x)Co_(y)O₂), LM (Li_(x)Mn₂O₄), and LNM(Li_(x)Ni_(1−y)Mn_(y)O₂). The prevailing commercial process forproducing NMC cathodes is the hydroxide co-precipitation process. In thestate-of-the-art industrial production method, ammonium ion is added toa solution of sulfates of nickel, manganese, and cobalt. Nickel,manganese, and cobalt cations form complex ions with ammonia. Caustic isthen added to induce decomposition of the transition metal ammoniumcomplexes and gradual precipitation of the hydroxide of NMC. Currentprocesses for the production of the transition metal sulfates startingmaterials (MSO₄) involve dissolving expensive, high grade, and highlypure primary nickel, manganese and cobalt powders in sulfuric acid(H₂SO₄). The hydroxide co-precipitation method can produce high-densitymicrospheres that are made of primary crystalline nano-platelets.

The NMC hydroxide is lithiated at about 930° C. in the presence ofLi₂CO₃. In the course of lithiation, two protons per formula unit of theNMC hydroxide are replaced by one lithium cation and the transitionmetal cations are oxidized from bivalent (+2) to trivalent (+3). Thestructure change from the NMC hydroxide to the lithiated material isvery small so that the microsphere morphology remains after calcination.

Although the lithiation process is short (usually 2-3 hours), thereexists a trace amount of a higher oxidation state manganese compound,Li₂MnO₃. This compound does not contribute to reversible storage unlessthe voltage is raised to over 4.5 V. In the Li—Mn—O system, Li₂MnO₃ ismore stable than LiMnO₂ in air at high temperatures. A metastable phaseLiMnO₂ can be synthesized only from lower oxidation state manganesecompounds, such as Mn(OH)₂ and MnCO₃. This is why NMC cathodes cannot bemade by the reaction of their corresponding oxides. Formation of Li₂MnO₃depletes the lithium content in the main NMC phase, and leads to lowstorage capacity. In order to obtain a high storage capacity, a slightexcess of lithium is added to compensate for loss due to the formationof the Li₂MnO₃ phase. It would be desirable to develop a process formaking NMC cathode materials that avoids formation of the Li₂MnO₃ phase.

The materials obtained by the hydroxide co-precipitation method have ahighly ordered structure (low cation mixing) and are of relatively highperformance in rate capacity and kinetics. However, the cathodesproduced by this method cannot give a high reversible capacity becausenearly 50% Li cations remain in the Li layer to stabilize the crystalstructure.

With an identical layered structure, the chemical properties of LiMO₂(M=Ni, Co, Mn) and, in particular, their transport of lithium ionsthrough intercalation and de-intercalation processes are quitedifferent. In LiMnO₂, most lithium ions can be de-intercalated becauseMn⁴⁺ is quite stable in the binary oxide MnO₂. However, the layeredstructure of LiMnO₂ tends to change to the spinel structure after mostof the lithium ions are de-intercalated. The reason is that the layeredstructure of MnO₂ is unstable since Van der Waals interactions of oxygenanions between layers are too weak to hold the structure togetherwithout Li ions. Spinel MnO₂ is a three-dimensional and stable structurebecause the Mn⁴⁺ ions occupy the sites of oxygen anions alternately. InLiCoO₂, only half of the lithium ions can be de-intercalated; the otherhalf of lithium ions remain to stabilize the layered structure.

Compared with LiMnO₂ and LiCoO₂, the Ni—O bond strength in LiNiO₂ isrelatively weak, especially at high temperatures. In Ni compounds, Niatoms have two oxidation states, i.e., Ni³⁺ and Ni²⁺. The Ni²⁺ ions havea similar size to Li⁺ (r_(Ni) ³⁺=0.056 nm, r_(Ni) ²⁺=0.068 nm, r_(Li)⁺=0.074 nm), and situate in the Li⁺ ion layers, blocking the path way ofLi⁺ transport. This is why LiNiO₂ suffers from poor performance at highrate.

In Ni-rich materials, a replacement of a small amount of Li by Ni in thelithium layers (weak cation mixing) gives larger reversible capacitybecause excess Ni stabilizes the structure by forming bonds between NiO₂slabs. As a result, a much higher fraction of Li ions are able toundergo reversible intercalation/de-intercalation. However, Ni atoms inthe Li layer can block the passage of Li⁺ transport, leading to poorperformance in rate capacity. Therefore, Ni²⁺ cations in lithium layersshould be controlled within a certain range in order to obtain higherperformance.

The term “cation mixing” is used herein to refer to the degree to whichtransition metal ions enter the lithium layers of NMC, LM, LNM, andother transition metal oxide cathode materials. A high degree of cationmixing indicates substantial substitution of transition metal ions inthe lithium layers and greater inhibition of lithium ion transport. Alow degree of cation mixing indicates little substitution of transitionmetal ion layers and a decrease in the fraction of lithium ionsavailable for ion transport due to utilization of a greater fraction oflithium ions to stabilize the structure. Cation mixing, expressed as anoccupancy factor of Ni on the Li site, can be determined by X-raydiffraction Rietveld profile refinements. The amount of Ni cationswithin the Li layers depends on the synthesis conditions.

In order to tailor the degree of cation mixing, there is a need for anew synthetic protocol. The synthesis methods disclosed herein enablethe control of the amount of cation mixing by programming reactionconditions. The conditions, such as precursors, duration of ballmilling, reaction temperatures and oxygen environments, are crucial indetermining crystalline phases, morphology, and cation mixing thatinfluence the electrochemical performance of the NMC, LM, LNM, andrelated cathode materials.

The disclosure presents methods for the production of cathode materialsfor lithium ion batteries. Manganese-containing cathode materials, suchas NMC (LiNi_(1−x−y)Mn_(x)Co_(y)O₂), LNM (Li_(x)Mn₂O₄) and LNM(Li_(x)Ni_(1−y)Mn_(y)O₂), are emphasized. These cathode materialsfeature high energy density. The method can also be used generally fortransition metal oxide materials. The process comprises reacting amixture of nickel, manganese, cobalt, and/or lithium precursors andcalcining to form an oxide.

The precursors for nickel, manganese, and cobalt are carboxylates.Preferred carboxylates are acetates and citrates. Other carboxylatesinclude formate, propionate, oxalate, malonate, isocitrate andacontitate. Carboxylates bonded to a given metal or to multiple metalsused in the preparations described herein are the same in someembodiments and differ in other embodiments. Precursors for lithiuminclude lithium hydroxide and lithium carbonate.

The metal carboxylate precursors are prepared from metal startingmaterials that enable a reduction in the cost of production of thecathode materials. Metal starting materials include pure metals andmetal compounds. Preferred starting materials are pure metals. As usedherein, “pure metal” refers to a starting material in which the metal ispresent in an elemental or zero valent state. The pure metals can be invarious physical forms (powder, flakes, particulate, nanoparticle, sheetetc.) and can be used directly without further treatment to producemetal carboxylate precursors that are subsequently reacted to form acathode material. Metal compounds include a metal in an oxidized state(cation). Representative metal compounds include metal oxides, metalhydroxides, and metal carbonates.

The metal carboxylate precursors are prepared by reacting a metalstarting material with a carboxylic acid. Reactions include liquid phasereactions and solid state reactions. Liquid phase reactions includemixing a metal starting material with a liquid carboxylic acid or asolution containing a carboxylic acid. Solid phase reactions includegrinding a metal starting material in the presence of a carboxylic acid.Mixed metal precursors are prepared by including two or more metalstarting materials in the reaction.

Carboxylate ligands in the metal carboxylate precursors includemonodentate and multidentate carboxylate ligands. Monodentatecarboxylate ligands have a single carboxylate functional group and bondto a single metal cation. Multidentate carboxylate ligands have two ormore carboxylate functional groups. Multidentate carboxylate ligands canbond with a particular metal cation at two or more bonding sites and/orcan bond with two or more different metal cations. Multidentatecarboxylate ligands include chelating carboxylate ligands. Acetate is anexample of a monodentate carboxylate and citrate is an example of amultidentate carboxylate.

Metal carboxylate precursors are reacted to form an oxide material.Reactions for forming the oxide material include liquid phase reactionsand solid state reactions. In liquid phase reactions, liquid phase metalcarboxylate precursors are combined, stirred and heated to form aslurry. The slurry is dried, ball milled, and calcined to form a metaloxide. A lithium precursor can be included in the slurry before dryingor added to the slurry after drying, but before ball milling. Solidphase reactions include ball milling solid phase metal carboxylateprecursors in the presence of a lithium precursor and then calcining toform a metal oxide. Metal carboxylate precursors with one or acombination of two or more metals are used in the liquid or solid phasereactions.

In one aspect, the process utilizes manganese precursors with bivalentmanganese (Mn²⁺) and provides conditions that prevent manganese fromoxidizing to higher oxidation states. The formation of byproducts, suchas Li₂MnO₃ in which manganese is in a high oxidation state is inhibited.

In one aspect, the process uses pure metals as starting materials formetal precursors. Pure metals are advantageous starting materialsbecause they are much less expensive than the metal sulfates used in thehydroxide co-precipitation process and can be used without purificationor preliminary processing. The time, complexity, and energy consumptionencountered in the hydroxide co-precipitation process are avoided.

The process further provides a method to tailor the degree of cationmixing through systematic control of reaction conditions. Reactionconditions, such as precursor selection, duration of ball milling,reaction temperatures and oxygen environments, are crucial indetermining the crystalline phases, product compounds, and cation mixingthat influence the electrochemical performance of NMC, LM, LNM, andother oxide electrodes. The present process provides great control overthe structure, composition, and oxidation states of transition metaloxide cathode materials.

Precursor Preparation

Manganese Precursors. The manganese precursors are critical tosolid-state synthesis of NMC materials because the oxidation state ofmanganese needs to be low (bivalent) to prevent formation of more highlyoxidized phases that reduce storage capacity. Carboxylate precursors areadvantageous to the formation of the NMC and other metal oxide materialsbecause the calcination process leads to evolution of reducing gasesthat act to prevent oxidation of manganese. Manganese carboxylates, suchas manganese citrate and manganese acetate, are preferred precursors.

To prepare manganese citrate, manganese flakes and citric acid are usedas the starting materials. Manganese flakes are crushed to small piecesand mixed with citric acid powder; then water is gradually added at roomtemperature or elevated temperatures (typically 20° C.-85° C.). Thegoverning reaction is:3Mn+2C₃H₅O(COOH)₃→Mn₃[C₃H₅O(COO)₃]₂+3H₂  (1)

The resulting product is a slurry that can be used directly as a metalprecursor for manganese-containing oxide material as described below.Alternatively, the slurry can be dried and used as a metal precursor.

To prepare manganese acetate, manganese flakes and acetic acid are usedas the starting materials. Crushed manganese flakes are loaded in amixer, and concentrated acetic acid is gradually added during mixing.Mixing can occur at room temperature or elevated temperature. Thegoverning reaction is:Mn+2CH₃(COOH)→Mn[CH₃(COO)]₂+H₂  (2)

The resulting product is a slurry. The slurry can be used directly or indried form as a metal precursor for the synthesis ofmanganese-containing metal oxide cathode materials.

Cobalt Precursors. Direct reaction of cobalt metal with citric acid oracetic acid proceeds relatively slowly. In the presence of an inorganicacid, however, cobalt metal reacts more readily with citric acid oracetic acid to produce cobalt citrate or cobalt acetate. As used herein,the term inorganic acid refers to an acid that lacks carbon.Representative inorganic acids include HNO₃, HCl, H₂SO₄, and HClO₄. Whennitric acid is used, the reactions are:3Co+2C₃H₅O(COOH)₃/(HNO₃)→Co₃[C₃H₅O(COO)₃]₂/[Co(NO₃)₂]+3H₂  (3)Co+2CH₃(COOH)/(HNO₃)→Co[CH₃(COO)]₂/[Co(NO₃)₂]+H₂  (4)

The slurry product is used directly or in dried form as a metalprecursor for cobalt-containing metal oxide materials

The compound starting material cobalt oxide reacts with citric acid oracetic acid to form cobalt citrate or acetate according to the followingreactions:3CoO+2C₃H₅O(COOH)₃→Co₃[C₃H₅O(COO)₃]₂+3H₂O  (5)CoO+2CH₃(COOH)→Co[CH₃(COO)]₂+H₂O  (6)

The kinetics of the reaction of cobalt oxide with carboxylic acids isslow because of the stability of cobalt oxides. Ball milling aids thekinetics by reducing the particle size of cobalt oxide startingmaterials and increasing mixing efficiency. Shorter reaction timesresult.

Other cobalt compound starting materials for cobalt metal precursorsinclude CO₃O₄, CoO, CoCO₃, and Co(OH)₂.

Nickel Precursors. Nickel metal reacts weakly with carboxylic acids. Inthe presence of an inorganic acid, however, nickel metal reacts morereadily with citric acid or acetic acid to produce nickel citrate ornickel acetate. When nitric acid is used, the reactions of nickel metalwith citric acid and acetic acid to form nickel citrate and nickelacetate are:3Ni+2C₃H₅O(COOH)₃/(HNO₃)→Ni₃[C₃H₅O(COO)₃]₂/[Ni(NO₃)₂]+3H₂  (7)Ni+2CH₃(COOH)/(HNO₃)→Ni[CH₃(COO)]₂/[Ni(NO₃)₂]+H₂  (8)

Oxides and other compounds of nickel can also be used as startingmaterials for nickel precursors. The reactions of citric acid and aceticacid with nickel oxide are:3NiO+2C₃H₅O(COOH)₃→Ni₃[C₃H₅O(COO)₃]₂+3H₂O  (9)NiO+2CH₃(COOH)→Ni[CH₃(COO)]₂+H₂O  (10)

Other nickel compound starting materials include Ni(OH)₂, NiCO₃, andNi_(1−x)O. Ball milling will facilitate the kinetics of reactions ofnickel compounds with carboxylic acids to shorten the reaction time.

Mixed Precursors. Mixed precursors include precursors that contain twoor more metals and/or two or more carboxylate groups. A pure metal or ametal compound, for example, can be reacted with two or more carboxylicacids (e.g. a combination of citric acid and acetic acid) to form amixed precursor. Similarly, two or more metal starting materials (puremetals or metal compounds) (e.g. pure metals or compounds of Ni and Co,Ni and Mn, or Co and Mn) can react with a carboxylic acid (e.g. citricacid or acetic acid) to form a mixed precursor. Also, two or more metalstarting materials (pure metals or metal compounds) can react with twoor more carboxylic acids (e.g. citric acid and acetic acid) to form amixed precursor.

In one aspect, a mixed precursor includes a compound that contains twoor more different metals (e.g. an acetate compound that includes Ni andCo). In another aspect, a mixed precursor includes a compound thatcontains two or more different carboxylate groups (e.g. a nickelcompound that includes acetate and citrate groups). In still anotheraspect, a mixed precursor includes a compound that contains two or moredifferent metals and two or more different carboxylate groups (e.g. acompound that contains nickel and cobalt along with citrate andacetate). In further aspects, the mixed precursor includes two or morecompounds, where the number and/or type of metal and/or carboxylategroup differs in the different compounds.

Reaction of solid phase metal precursors to form metal oxides is apotentially facile and low-cost manufacturing technology that has beensuccessfully applied to industrial production of many metal oxides. Thetechnology is especially applicable to the production of metal oxideshaving constituent metals with stable oxidation states at the elevatedtemperatures typically used for solid state synthesis. LiCoO₂, forexample, has a stable +3 oxidation state for Co at high temperature andcan be readily produced in a solid state reaction from solid phasecobalt precursors. Single phase LiCoO₂ with a layered structure can formhigh-density nanocrystals. Many technical challenges, however, haveremained in the preparation of manganese-containing oxide materials bysolid-state reactions. Manganese is a difficult metal constituent tocontrol because manganese (1) readily transforms between any of multipleoxidation states, (2) tends to form of multiple crystalline phases thatdiffer in stoichiometry, (3) is highly sensitive to reaction conditions,and (4) frequently leads to non-uniform reaction products. Due to alimited understanding of the reaction chemistry of manganese,solid-state reaction technology has not yet been effectively utilized toproduce NMC and other manganese-containing oxide materials. Examplesdescribed herein demonstrate that NMC materials can be successfullyproduced by using a solid-state process when the manganese precursorsdescribed herein are used in the reaction.

Preparation of Transition Metal Oxides

Various reaction schemes for preparing transition metal oxides from themetal precursors described herein are described below. Transition metaloxides that can be prepared using the methods described herein includeLi_(x)Ni_(1−y−z)Mn_(y)Co_(z)O₂ (NMC) (where x is in the range from 0.80to 1.3, y is in the range from 0.01 to 0.5, and z is in the range from0.01 to 0.5), Li_(x)Mn₂O₄ (LM), and Li_(x)Ni_(1−y)Mn_(y)O₂ (LNM) (wherex is in the range from 0.8 to 1.3 and y is in the range from 0.0 to0.8). Although not explicitly listed, other transition metal oxidecompositions can be similarly prepared using the methods disclosedherein.

The reaction schemes and examples described below will emphasize NMC asan illustrative transition metal oxide material. Analogous schemes fortransition metal oxides in general are readily recognizable and can bereadily implemented by those of ordinary skill in the art.

Reaction schemes to make NMC materials include:

Scheme I: Carboxylate precursors of manganese, nickel, and cobalt madefrom pure metal starting materials are used to make NMC. Metalcarboxylate precursors include manganese citrate, manganese acetate,nickel citrate, nickel acetate, cobalt citrate, and cobalt acetate. Inone aspect, the metal carboxylate precursors are made from a reaction ofpure metals with a carboxylic acid. In another aspect, the metalcarboxylate precursors are made from a reaction of a metal compound witha carboxylic acid. In one aspect, the metal carboxylate precursorsinclude residual acid and/or an acid bonded to or complexed with ametal. The carboxylate precursors can be prepared separately and thencombined (as slurries and/or solids) in a reaction to form a metaloxide. Alternatively, the starting materials for the differentcarboxylate precursors can be combined and reacted to form a metaloxide, where the carboxylate precursors form as intermediates in thereaction. In one aspect, the reaction to form a metal oxide includesball milling. In another aspect, the reaction to form a metal oxideincludes calcination.

Scheme II: Carboxylate precursors of nickel and cobalt made from metalcompound starting materials and a manganese carboxylate precursor madefrom pure manganese metal are used to make NMC. Metal compound startingmaterials for nickel and cobalt include oxides, carbonates, andhydroxides. Oxides are preferred metal compound starting materials. Thecarboxylate precursors can be prepared separately and then combined (asslurries and/or solids) in a reaction to form a metal oxide.Alternatively, the starting materials for the different carboxylateprecursors can be combined and reacted to form a metal oxide, where thecarboxylate precursors form as intermediates in the reaction. In oneaspect, the reaction to form a metal oxide includes ball milling. Inanother aspect, the reaction to form a metal oxide includes calcination.

The kinetics of solid state reaction at high temperature are closelyrelated to the diffusion of particles. Application of heat enhances therate of diffusion, and thus increases the rate of the reaction. Hightemperatures promote the formation of Li₂MnO₃ and a high degree ofcation mixing, whereas moderate temperatures and oxidizing atmospheresfavor the formation of lower cation mixing because of the stabilizationof Ni³⁺. Ball milling can reduce particle size and increase theefficiency of mixing, thus increasing kinetics.

Lithiation and Calcination: Formation of lithium cathode materialsrequires lithiation of transition metal oxide compounds made with themethods described herein. Lithiation is accomplished with a lithiumprecursor. A lithium precursor is a compound that includes lithium.Preferred lithium precursors include Li₂CO₃ and LiOH·H₂O. In one aspect,lithiation is accomplished by combining one or more metal precursorswith a lithium precursor in a ball milling jar. A small amount ofacetone or other liquid may also be added as a wetting agent to the jarbecause wet-milling is much more efficient than dry-milling. Theresulting mixture is slowly heated to e.g. 600-950 □C, and kept at thattemperature for ten to twenty hours. In one aspect, calcination occursin air. Representative calcination conditions are presented in theexamples below.

During the solid-state reactions that are induced by calcination, themetal precursors decompose to form nanoparticles. An air environmentcontrolling condition is dependent on the selection of the precursors.When metal carboxylate precursors are used in the solid state reaction,decomposition releases CO, CO₂, and H₂O. As noted above, residualnitrate groups are present in some embodiments of metal carboxylateprecursor and lead to production of NO_(x) and O₂ during decomposition.NO_(x) and/or O₂ may react with CO. The decomposition products contain abalance of reducing and oxidizing species that inhibit oxidation ofmanganese to Mn⁴⁺ or higher in the metal oxide product while alsoinhibiting reduction of nickel to Ni²⁺ in the metal oxide product. Thepresence of the preferred oxidation states Mn³⁺ and Ni³⁺ in the metaloxide product is increased.

For nickel-rich NMC materials, high temperatures enhance the rate of thereaction, but increase the degree of cation mixing whereas moderatetemperatures favor the formation of an ordered structure with lesscation mixing, but this needs a prolonged reaction time. Hightemperatures and prolonged reaction time increase the formation ofLi₂MnO₃. Citrates and acetates increase the atomic level connectionsamong Ni, Mn, Co and Li cations or atoms through chelating, therebyfacilitating a drastic increase in the reaction rate. The degree ofinterconnectedness of metal cations or atoms can be controlled throughthe ratio of acetate and citrate groups present in the reaction mixture(or more generally, the ratio of monodentate and multidentate groups).In one aspect, citrate (and other multidentate carboxylate) groups arecapable of forming extending chains or networks that include multiplemetal cations or atoms to form an interconnected structure. Acetate (andother monodentate carboxylate) groups bond to a single metal cation oratom and act to disrupt chains or extended networks to promote formationof a less interconnected structure.

The ratio of multidentate carboxylate groups (e.g. citrate) tomonodentate carboxylate groups (e.g. acetate) in the reaction mixtureused to form a metal precursor, mixed metal precursor or metal oxide isin the range from 0.25-2.0, or in the range from 0.50-1.5, or in therange from 0.7-1.3, or in the range from 0.85-1.2.

Metal citrates and acetates (and other metal carboxylates) decompose toform nanoparticles that can enhance the rate of diffusion. Furthermore,decomposition of carboxyl groups releases reducing gases to protectmanganese from oxidizing. In order to avoid oxidizing manganese, the airflow rate should be controlled during calcinations. In addition, ballmilling can reduce particle sizes, and wet milling increases themobility of particles to enhance mixing efficiency, thereby reducing thereaction time. The synthesis conditions greatly affect the structuresand performances of materials.

Metal oxides prepared from the metal precursors described herein includeLi_(x)Ni_(1−y−z)Mn_(y)Co_(z)O₂, where x is in the range from 0.80 to1.3, y is in the range from 0.01 to 0.5, and z is in the range from 0.01to 0.5; and Li_(x)Mn₂O₄, where x is in the range from 0.8 to 1.3; andLi_(x)Ni_(1−y)Mn_(y)O₂, where x is in the range from 0.8 to 1.3 and y isin the range from 0.0 to 0.8.

The present invention also provides a method for directly recovering andre-synthesizing an NMC cathode from a waste lithium ion battery,avoiding a complex separation process. In particular, the process uses acarboxylic acid to reduce manganese present in a higher oxidation state(e.g. Mn⁴⁺) in the waste to generate new cathode material with manganesepresent in a lower oxidation state (e.g. Mn²⁺). In more particular, thecathode can be recovered by sintering the waste in a reducingenvironment such as hydrogen and carbon monoxide.

Example 1. Preparation of Mixed Manganese Precursor Solution. 20.0 gcrushed electrolytic Mn flakes, 20.0 g acetic acid and 20.0 g citricacid were put in a beaker. 200 ml of distilled water was graduallyadded. The mixture was heated at 95-100° C. until the Mn was completelyreacted. The product was a liquid phase mixed manganese precursor. Thefinal weight of the Mn precursor solution was 110.4 g (18.3 wt % Mn).

Example 2. Preparation of Nickel Acetate Precursor Solution. 394.5 gnickel balls (3-10 mm diameter), 100 ml of distilled water, 20 g aqueousHNO₃ (67 wt %), 15 g acetic acid and 15 g citric acid were placed in aPTFE beaker with a cap. The beaker was heated at 95-100° C. for fivehours. While heating, an additional 200 ml of distilled water wasgradually added to prevent the reaction mixture from drying out. Partialreaction of the nickel balls occurred during the reaction time. Theunreacted portion of the nickel balls was separated from the solutionand rinsed three times with 10 ml of distilled water. The rinse productwas added back to the solution. The unreacted nickel balls were thenfurther rinsed with a large amount of water and dried. The final weightof the unreacted portion of the nickel balls was 375.3 g, which meansthat the net nickel weight in the product nickel acetate precursorsolution was 17.2 g. The final weight of the nickel precursor solutionwas 200.5 g (8.58 wt % of which was nickel).

Example 3. Preparation of Cobalt Acetate Precursor Solution. 209.9 gcobalt flakes, 100 ml distilled water, 17 g aqueous HNO₃ (67 wt %), and20 g acetic acid were placed in a PTFE beaker with a cap. The beaker washeated at 95-100° C. for five hours. While heating, an additional 200 mldistilled water was gradually added to prevent the reaction mixture fromdrying out. Partial reaction of the cobalt flakes occurred during thereaction time. The unreacted portion of the cobalt flakes was separatedfrom the solution and rinsed with 10 ml distilled water. The rinseproduct was added back to the solution. The unreacted cobalt flakes werethen further rinsed with a large amount of water and dried. The finalweight of the unreacted cobalt flakes was 193.1 g, which meant that thenet cobalt weight in the cobalt acetate precursor solutions was 15.9 g.The final weight of the cobalt acetate precursor solution was 169.9 g(9.36 wt % of which was cobalt).

Example 4. Preparation of NMC622 (LiNi_(0.6)Mn_(0.2)Co_(0.2)O₂). 123.1 gof the nickel acetate precursor solution (Example 2), 18.0 g of themixed manganese precursor solution (Example 1), and 37.8 g of the cobaltacetate precursor solution (Example 3) were put in a beaker with a cap.The beaker was heated at 95-100° C. for 1 hour while stirring. 14.5 g ofLiOH·H₂O was then added with stirring while maintaining the temperatureat 95-100° C. to form a viscous slurry. The resulting slurry was driedat 130° C. overnight. The dried slurry was placed in a one-liter jar. 1kg of a grinding medium (ZrO₂, average particle size ⅜″) and 70 g ofacetone were added to the jar. The dried slurry was then milled in thejar for 5 hours. The milled product was dried in air and loaded in aAl₂O₃ crucible for calcination. Calcination included increasing thetemperature of the crucible from room temperature to 950° C. over a timeperiod of 3 hours. The crucible was then held at 950° C. for 10 hours,cooled from 950° C. to 600° C. over a time period of 5 hours, kept at600° C. for 5 hours, and then cooled to room temperature over a timeperiod of 5 hours. The final product was ground and characterized byXRD, SEM, and electrochemical half-cell testing.

Example 5. Preparation of a Mixed Precursor for NMC532(LiNiI_(0.5)Mn_(0.3)Co_(0.2)O₂). 8.8 g Ni powder (with an averagediameter of 3 μm-7 μm), 3.5 g Co powder (200 mesh), 4.9 g crushed Mnpowder, 18.9 g citric acid and 18 g acetic acid were placed in a beakerand mixed. The metal powders had an average diameter of 3 μm-7 μm. 100ml of aqueous HNO₃ solution (7 wt %) was gradually added at roomtemperature and the mixture was heated at 95-100° C. for 3 hours whilestirring. During the 3-hour reaction time period, an additional 100 mldistilled water was added to prevent the reaction mixture from dryingout. The resulting slurry was dried overnight.

Example 6. Preparation of NMC532 (LiNi_(0.5)Mn_(0.3)Co_(0.2)O₂). Themixed precursor for NMC532 described in Example 5 was placed in aone-liter jar. 12.7 g Li₂CO₃, 1 kg of grinding medium (ZrO₂, averageparticle size ⅜″) and 70 g of acetone were added to the jar. Thecontents of the jar were milled for 5 hours. The milled product wasdried overnight in air and loaded in a Al₂O₃ crucible for calcination.To calcine, the crucible was heated from room temperature to 950° C.over a time period of 3 hours. The crucible was then held at 950° C. for10 hours, cooled from 950° C. to 600° C. over a time period of 5 hours,kept at 600° C. for 5 hours, and then cooled to room temperature over atime period of 5 hours. The final product was ground and characterizedby XRD (FIG. 1 ), SEM (FIG. 3 and FIG. 4 ), and electrochemicalhalf-cell testing (FIG. 7 (charge and discharge capacity over two cyclesat 0.1 C rate) and FIG. 8 (rate performance at various rates (0.1 C, ⅓C, and 1 C)).

Example 7. Preparation of a Mixed Precursor for NMC701515(LiN_(0.7)Mn_(0.15)Co_(0.15)O₂). 12.3 g Ni powder (with an averagediameter of 3 μm-7 μm), 2.7 g Co powder (200 mesh), 2.5 g crushed Mnpowder, 15.0 g citric acid and 18 g acetic acid were placed in a beakerand mixed. The metal powders had an average diameter of 3 μm-7 μm. 100ml of aqueous HNO₃ solution (12 wt %) was gradually added at roomtemperature and the mixture was heated at 95-100° C. for 3 hours whilestirring. During the 3-hour reaction time period, an additional 120 mldistilled water was added to prevent the reaction mixture from dryingout. The resulting slurry was dried overnight.

Example 8. Preparation of NMC701515 (LiNI_(0.7)Mn_(0.15)Co_(0.15)O₂).The mixed precursor for NMC701515 described in Example 7 was placed in aone-liter jar. 12.7 g Li₂CO₃, 1 kg of grinding medium (ZrO₂, averageparticle size ⅜″) and 70 g of acetone were added to the jar. Thecontents of the jar were milled for 5 hours. The milled product wasdried overnight in air and loaded in a Al₂O₃ crucible for calcination.To calcine, the crucible was heated from room temperature to 93° C. overa time period of 3 hours. The crucible was then held at 930° C. for 5hours, cooled from 930° C. to 800° C. over a time period of 5 hours,kept at 800° C. for 30 hours, cooled from 800° C. to 750° C. over a timeperiod of 2 hours, kept at 750° C. for 20 hours, cooled from 750° C. to600° C. over a time period of 5 hours, kept at 600° C. for 5 hours, andthen cooled to room temperature over a time period of 5 hours. The finalproduct was ground and characterized by XRD (FIG. 2 ).

Example 9. Preparation of a Mixed Precursor for NMC811(LiNi_(0.8)Mn_(0.1)Co_(0.1)O₂). 14.1 g Ni powder (with an averagediameter of 3 μm-7 μm), 1.8 g Co powder (200 mesh), 1.6 g crushed Mnpowder, 15.0 g citric acid and 18 g acetic acid were placed in a beakerand mixed. The metal powders had an average diameter of 3 μm-7 μm. 100ml of aqueous HNO₃ solution (12 wt %) was gradually added at roomtemperature and the mixture was heated at 95-100° C. for 3 hours whilestirring. During the 3-hour reaction time period, an additional 120 mldistilled water was added to prevent the reaction mixture from dryingout. The resulting slurry was dried overnight.

Example 10. Preparation of NMC811 (LiNi_(0.8)Mn_(0.1)Co_(0.1)O₂). Themixed precursor for NMC811 described in Example 9 was placed in aone-liter jar. 12.7 g Li₂CO₃, 1 kg of grinding medium (ZrO₂, averageparticle size ⅜″) and 70 g of acetone were added to the jar. Thecontents of the jar were milled for 5 hours. The milled product wasdried overnight in air and loaded in an Al₂O₃ crucible for calcination.To calcine, the crucible was heated from room temperature to 930° C.over a time period of 3 hours. The crucible was then held at 930° C. for5 hours, cooled from 930° C. to 800° C. over a time period of 5 hours,kept at 800° C. for 30 hours, cooled from 800° C. to 750° C. over a timeperiod of 2 hours, kept at 750° C. for 20 hours, cooled from 750° C. to600° C. over a time period of 5 hours, kept at 600° C. for 5 hours, andthen cooled to room temperature over a time period of 5 hours. The finalproduct was ground and characterized by XRD (FIG. 2 ).

Example 11. Preparation of a Mixed Manganese Precursor. 3.3 g Mn flakeswere crushed and ground in a mortar. 3.6 g acetic acid and 3.9 g citricacid were then added with mixing. 10 ml water was gradually added duringmixing to promote the reaction. The final product was a solid phasemixed Mn precursor in the form of a powder.

Example 12. Preparation of a Mixed Nickel-Cobalt Precursor. 13.9 g ofNi_(x)O (76 wt % Ni), 4.5 g of CoO, 14.4 g of acetic acid and 15.1 g ofcitric acid were placed in a mortar and ground for 30 min. The mixturewas transferred into a container sealed with a cap and left overnight todry.

Example 13. Preparation of NMC622 (LiNI_(0.6)Mn_(0.2)Co_(0.2)O₂). Themixed manganese precursor of Example 11, the mixed nickel-cobaltprecursor of Example 12, 12.7 g of Li₂CO₃, 1 kg of grinding medium(ZrO₂, average particle diameter ⅜″) and 70 g acetone were placed in aone-liter jar and ball-milled for 5 hours. The milled product was driedin air and loaded in a Al₂O₃ crucible for calcination. To calcine, thecrucible was heated from room temperature to 950° C. over a time periodof 3 hours. The crucible was then held at 950° C. for 10 hours, cooledfrom 950° C. to 600° C. over a time period of 5 hours, kept at 600° C.for 5 hours, and then cooled to room temperature over a time period of 5hours. The final product was ground and characterized by XRD (FIG. 1 ),SEM (FIG. 5 and FIG. 6 ), and electrochemical half-cell testing (FIG. 9(charge and discharge capacity at various rates (0.1 C, ⅓ C, and 1 C))and FIG. 10 (charge-discharge performance over multiple cycles)).

Example 14. Preparation of LiNi_(0.5)Mn_(0.2)Co_(0.2)Fe_(0.1)O₂. Thisexample illustrates the versatility of the method described herein forpreparing new compositions for lithium ion cathode materials. Inparticular, this example illustrates a modified form of the NMC familyof materials to include other transition metal cations. Incorporation ofFe is illustrated, but the method applies generally to other transitionmetals.

NMC materials with ferrous ion (Fe²⁺) are difficult to synthesize withco-precipitation and other prior art methods because the presence offerrous ion promotes cation mixing. Ferrous ion, for example, has agreater tendency to enter the planar Li⁺ layer of the structure thannickel. With the present method, NMC materials containing ferrous ionand a low degree of cation mixing can be prepared.

Preparation of a Mixed Precursor forLiNI_(0.5)Mn_(0.2)Co_(0.2)Fe_(0.1)O₂). 8.8 g Ni powder (with an averagediameter of 3 μm-7 μm), 3.5 g Co powder (200 mesh), 3.3 g crushed Mnpowder, 1.7 g Fe powder, 18.9 g citric acid and 18 g acetic acid wereplaced in a beaker and mixed. The metal powders had an average diameterof 3 μm-7 μm. 100 ml of aqueous HNO₃ solution (7 wt %) was graduallyadded at room temperature and the mixture was heated at 95-100° C. for 3hours while stirring. During the 3-hour reaction time period, anadditional 100 ml distilled water was added to prevent the reactionmixture from drying out. The resulting slurry was dried overnight. 12.7g Li₂CO₃, 1 kg of grinding medium (ZrO₂, average particle size ⅜″) and70 g of acetone were added to the jar. The contents of the jar weremilled for 5 hours. The milled product was dried overnight in air andloaded in a Al₂O₃ crucible for calcination. To calcine, the crucible washeated from room temperature to 930° C. over a time period of 3 hours.The crucible was then held at 930° C. for 5 hours, cooled from 930° C.to 800° C. over a time period of 5 hours, kept at 800° C. for 30 hours,cooled from 800° C. to 750° C. over a time period of 2 hours, kept at750° C. for 20 hours, cooled from 750° C. to 600° C. over a time periodof 5 hours, kept at 600° C. for 5 hours, and then cooled to roomtemperature over a time period of 5 hours. The final product was groundand characterized by XRD (FIG. 11 ).

Example 15. Preparation of a Mixed Precursor for LiNi_(0.7)Mn_(0.3)O₂.12.3 g Ni powder (with an average diameter of 3 μm-7 am), 4.9 g crushedMn powder, 15.0 g citric acid and 18 g acetic acid were placed in abeaker and mixed. 100 ml of aqueous HNO₃ solution (12 wt %) wasgradually added at room temperature and the mixture was heated at95-100° C. for 3 hours while stirring. During the 3-hour reaction timeperiod, an additional 120 ml distilled water was added to prevent thereaction mixture from drying out. The resulting slurry was driedovernight. 12.7 g Li₂CO₃, 1 kg of grinding medium (ZrO₂, averageparticle size ⅜″) and 70 g of acetone were added to the jar. Thecontents of the jar were milled for 5 hours. The milled product wasdried overnight in air and loaded in an Al₂O₃ crucible for calcination.To calcine, the crucible was heated from room temperature to 950° C.over a time period of 5 hours. The crucible was then held at 950° C. for10 hours, cooled from 950° C. to 800° C. over a time period of 5 hours,kept at 800° C. for 30 hours, cooled from 800° C. to 750° C. over a timeperiod of 2 hours, kept at 750° C. for 20 hours, cooled from 750° C. to600° C. over a time period of 5 hours, kept at 600° C. for 5 hours, andthen cooled to room temperature over a time period of 5 hours. The finalproduct was ground and characterized by XRD (FIG. 12 ).

The XRD data shown in FIGS. 1, 2 and 11 indicate that the NMC productsexhibit a low degree of cation mixing. Cation mixing can be the ratio ofthe intensity of the (003) diffraction peak (I₀₀₃) to the intensity ofthe (104) diffraction peak (I₁₀₄). The (003) and (104) diffraction peaksare labeled in FIGS. 1, 2, and 11 . As the degree of cation mixingincreases, the ratio I₀₀₃/I₁₀₄ decreases. A ratio I₀₀₃/I₁₀₄ less than1.20 indicates a high degree of cation mixing and poor electrochemicalperformance of the metal oxide when used as a cathode material forlithium ion batteries. The I₀₀₃/I₁₀₄ ratios for the materials shown inFIGS. 1 and 2 are 1.38 (LiNi_(0.6)Mn_(0.2)Co_(0.2)O₂), 1.55(LiNi_(0.8)Mn_(0.1)Co_(0.1)O₂), 1.86 (LiNi_(0.5)Mn_(0.3)Co_(0.2)O₂), and1.87 (LiNi_(0.7)Mn_(0.15)Co_(0.15)O₂). Materials prepared by the methodsdescribed herein have an intensity ratio I₀₀₃/I₁₀₄ greater than 1.30, orgreater than 1.40, or greater than 1.50, or greater than 1.60, orgreater than 1.70, or greater than 1.80, or in the range from 1.35-1.95,or in the range from 1.45-1.90, or in the range from 1.55-1.85.

A first aspect of the disclosure is a method for forming an oxidematerial comprising:

reacting a first precursor with a second precursor, said first precursorcomprising a first compound, said first compound including a first metalbonded to a first carboxylate group and a second carboxylate group, saidsecond precursor including a second compound, said second compoundincluding a second metal bonded to a third carboxylate group

A second aspect of the disclosure is the first aspect, wherein saidfirst carboxylate group is acetate or citrate.

A third aspect of the disclosure is the first or second aspect, whereinsaid second carboxylate group is citrate or acetate.

A fourth aspect of the disclosure is any of the first through thirdaspects, wherein said third carboxylate group is acetate, citrate,formate, propionate, oxalate, malonate, isocitrate or acontitate.

A fifth aspect of the disclosure is any of the first through fourthaspects, wherein said first metal is Ni or Co.

A sixth aspect of the disclosure is any of the first through fifthaspects, wherein said second metal is Mn.

A seventh aspect of the disclosure is any of the first through sixthaspects, wherein said third metal is Al, Fe, Cu, Zn, Ti, or Zr.

An eighth aspect of the disclosure is any of the first through seventhaspects, wherein said reacting occurs at a temperature between 600 to950° C.

A ninth aspect of the disclosure is any of the first through eighthaspects, wherein said reacting comprises ball milling a mixture of saidfirst precursor and said second precursor.

A tenth aspect of the disclosure is any of the first through ninthaspects, wherein said reacting produces a product comprising:Li_(x)Ni_(1−y−z)Mn_(y)Co_(z)O₂,

-   -   wherein x is in the range from 0.80 to 1.3, y is in the range        from 0.01 to 0.5, and z is in the range from 0.01 to 0.5.

An eleventh aspect of the disclosure is any of the first through ninthaspects, wherein said reacting produces a product comprising:Li_(x)Mn₂O₄

-   -   wherein x is in the range from 0.8 to 1.3.

A twelfth aspect of the disclosure is any of the first through ninthaspects, wherein said reacting produces a product comprising:Li_(x)Ni_(1−y)Mn_(y)O₂

-   -   wherein x is in the range from 0.8 to 1.3 and y is in the range        from 0.0 to 0.8.

A thirteenth aspect of the disclosure is a method of making acarboxylate compound comprising:

-   -   reacting a first pure metal with a first carboxylic acid in the        presence of an inorganic acid.

A fourteenth aspect of the disclosure is the thirteenth aspect, whereinsaid first pure metal comprises Ni, Co, or Mn.

A fifteenth aspect of the disclosure is the thirteenth or fourteenthaspect, wherein said inorganic acid is selected from the groupconsisting of nitric acid, hydrochloric acid, sulfuric acid, andperchloric acid.

A sixteenth aspect of the disclosure is any of the thirteenth throughfifteenth aspects, wherein said inorganic acid is nitric acid.

A seventeenth aspect of the disclosure is a method of making acarboxylate compound comprising:

-   -   reacting a first metal compound with a first carboxylic acid,        said reacting including ball milling a mixture of said first        metal compound and said first carboxylic acid.

An eighteenth aspect of the disclosure is the seventeenth aspect,wherein said first metal compound is a metal oxide or metal carbonate.

A nineteenth aspect of the disclosure is the seventeenth or eighteenthaspect, wherein said first metal compound comprises Ni, Co or Mn.

A twentieth aspect of the disclosure is any of the seventeenth throughnineteenth aspects, wherein said first metal compound is derived from awaste lithium ion battery.

Those skilled in the art will appreciate that the methods and designsdescribed above have additional applications and that the relevantapplications are not limited to those specifically recited above. Also,the present invention may be embodied in other specific forms withoutdeparting from the essential characteristics as described herein. Theembodiments described above are to be considered in all respects asillustrative only and not restrictive in any manner.

What is claimed is:
 1. A method of making a carboxylate compoundcomprising: reacting a first pure metal with citric acid in the presenceof an inorganic acid.
 2. The method of claim 1, wherein said first puremetal comprises Ni, Co, or Mn.
 3. The method of claim 1, wherein saidinorganic acid is selected from the group consisting of nitric acid,hydrochloric acid, sulfuric acid, and perchloric acid.
 4. The method ofclaim 1, wherein said inorganic acid is nitric acid.
 5. The method ofclaim 1, wherein the reacting occurs in the presence of a second puremetal, the second pure metal reacting with the citric acid.
 6. Themethod of claim 5, wherein the first pure metal is Co and the secondpure metal is Ni.
 7. The method of claim 6, wherein the reacting occursin the presence of a third metal, the third metal reacting with thecitric acid, the third metal being Al, Fe, Cu, Zn, Ti, or Zr.
 8. Themethod of claim 5, wherein the first pure metal is Co and the secondpure metal is Mn.
 9. The method of claim 8, wherein the reacting occursin the presence of a third metal, the third metal reacting with thecitric acid, the third metal being Al, Fe, Cu, Zn, Ti, or Zr.
 10. Themethod of claim 5, wherein the first pure metal is Mn and the secondpure metal is Ni.
 11. The method of claim 10, wherein the reactingoccurs in the presence of a third metal, the third metal reacting withthe citric acid, the third metal being Al, Fe, Cu, Zn, Ti, or Zr. 12.The method of claim 1, wherein the reacting occurs in the presence ofacetic acid, the first pure metal further reacting with the acetic acid.13. The method of claim 12, wherein the reacting occurs in the presenceof a second pure metal, the second pure metal differing from the firstpure metal, the second metal reacting with the citric acid or the aceticacid.
 14. The method of claim 13, wherein the first pure metal is Co andthe second pure metal is Ni.
 15. The method of claim 13, wherein thefirst pure metal is Co and the second pure metal is Mn.
 16. The methodof claim 13, wherein the first pure metal is Mn and the second puremetal is Ni.